Chair backrest



FIG. 1 is a perspective view of a chair backrest showing my new design;

FIG. 2 is a front elevational view of FIG. 1;

FIG. 3 is a rear elevational view of FIG. 1;

FIG. 4 is a left side elevational view of FIG. 1, the opposite side being a mirror image thereof;

FIG. 5 is a top plan view of FIG. 1;

FIG. 6 is a bottom plan view of FIG. 1; and,

FIG. 7 is another perspective view of FIG. 1. The broken lines showing the remainder of the chair are for illustrative purposes only and form no part of the claimed design. 

The ornamental design for chair backrest, as shown and described. 